Carrier-wave telephone system



June 12, 1928. 1,673,548 C. A. BODDIE CARRIER WAVE TELEPHONE'SYSTEMFiled Aug. 18, 1923 wnusssss; INVENTOR C/armceflfioddle.

' TTORNEY Patented June 12, 1928.

UNITED STATES 1,673,548 PATENT ounce.

CLARENCE A. 120mm, 025 WILKINSIBTURG, PENNSYLVANIA, assmnoa T0 mam HOUSEnnso'raxc & MANUFACTURING COMPANY. ACOIRPORA'I'ION or PENNSYL- VANIA.

oanamaswavn TELEPHONE .sYsTEm.

Application filed August 18, 1923. Serial No. 658,041. l

My invention relates to carrier-wave tele phone systems and particularlyto the transmission of signals by radio-frequency elecltl'lc current.

Broadly speaking, the object of my invention is to provide means for theduplex operation of radio signalling systems.

More specifically, the object of my invention is to provide acompensatingmeansfor transferring energy from a radio sending equipmentto an adjacent radio receiving equipment in such way as to cause thetrans ferred energy to neutralize energy transferred from the radiosending set to the adjacent radio receiving set byiwayof theirrespective aerials and the ether.

In the prior art of transmission of signals by radio communicationmethods, it hasbeen customary in a great many cases to shut down the.receiving apparatus during the time in which it was desired to sendsignals and likewise to shut down the sendingapparatus when it wasdesired to receive signals. It .was found that the relatively tremendousamount of energy in the sending system produced a decided influence onthe adjacent receiving system. So much transferred to the receivingsystem when the sending system was in operation under ordinaryconditions as to make it impossible to .necei ve signals from adistance. The energy thus received would render. receiving tubesinoperative in case vacuum tube detectors were employed, and in the case.otanyother .deteotor would entirely overpower signals from the remotestation, Because ofthis tact, one-way operation only was ordinarilypossible.

A number of attempts have been made "by inventors to find means ofovercoming this difliculty, and thereby to permit duplex, or two-way,.operationso that it would-not be necessary to put the sending system.out oi operation when it was desired to receive signals. This objectwas especially .deslred in connection with radio telephone systems, inwhich duplex operation is very desirable. This object has been partiallyattained in the prior, art in number for ways. 'lhe receiving stationand the sending station .may be geographically separated asubstaaitiald'stance and connected by a suitable transmission line, in which caseduplex operation is to a certain extent possible, although .interterenceis not entirely preenergy was vented. Some side tones remain regardlessof the distance of separation of the stations. Attempts have been madeto use the same aerial tor both receiving and sending. This has beendone by means of a double sending helix. One "half of the helix isconnected through the aerial and ground circuit and the other half isconnected through an inductance andcapacitance equivaleutto theinductance and capacity of the-aerial system. I This inductance andcapacity assembly forms what may be called a dununy aerial, whichabsorbs one-half oi" the input energy. In doing so it produces currentsin the second half of the winding helix which are equal and opposite inphase to currents in the first half. Each ofthese currents then neutrliz'es the etiect ofthe other upon an inductively coupled coilin thereceiving circuit. This arrangement permits the incoming sig nal currentto be received-by the receiving system and does not; Permit theloi'rial'power current to interfere. This system is objectionablebecauseof thetact that it wastes "one half of the total sending energy.

Another system, separates the receiving and sending-stations by asubstantial geographical distance and connects them electrically by asinge transmission line, which line serves to carry audio frequencycontrol current and also carries a small amount of" radio frequencyenergy from the sending apparatus to thereceiving apparatus for thepurpose of neutralizing the enei'gy'picked up by the receiving aerialhaving radiated from the sending aerial. This system also givesapproximate neutralization but it is objectionable because of therequired goo graphical separation and because it does not give completecompensation. H

It has been proposed to employ two antenna syste1ns, one for receivingand one for sending, and a single-circuit inductive energy a transferconnection between sending and receiving apparatus. "lhissystem givesonly the form of alternating currentl'las a specificphase relation tocurrent in the sending aerial. To neutralize the et'fec.t of this energin producing interference, a pre .cisely equal amount ot'energy at thesame trequency and in precise phase opposition may be impressed upon thereceiving system. If this is done, complete neutralization will beobtained. My invention efiects this result by means of a plurality ofconductive channels from the sending apparatus to the receivingapparatus without requiring a geographic separation between sending andreceiving stations.

Other objects and structural details of my invention will be apparentfrom the following description and claims when read in connection withthe accompanying drawings, wherein I Figure l, is a diagrammatic sketchof apparatus and circuit connections embodying my invention and Fig. 2is a vector diagram of the phase relations of the currents in thereceiving apparatus.

in F i". 1, a sending system aerial 1 is located adjacent to thereceiving system aerial Aerial l is connected to a tuning helix 3 by alead-in wire 4;. A ground 5 is provided and connected by a lead wire 6to helix 3 at a point above its bottom turn. This point is located inaccordance with the desired wave, length or sending frequency. Energy istransferred to this coil from any convenient source as indicated by theprior art. This source may be a triode tube oscillator, with or withouta modulator, according to whether or not it is desired to send voicemodulated signals, or the source of energy may be an arc, spark, orother suitable source.

Receiving aerial 2 is connected to a suitable adjacent receiving set 7.The details of this set are not important. In the diagrammatic sketch, asimple system is shown com prising a series condenser 8, a tuninginductance 9, a triode detector 11. with its asso ciated grid leak andcondenser 12, an A" battery 13, a B battery 14, telephones 15 or othersignal receiver, lead-in wire 16, serving as connection between aerial 2and receiving apparatus and lead wire 17 connecting receiving apparatus7 to'the ground 18. A connection is made between receiving set Tat point19, which is the point of connection between the series condenser andthe tuning helix, and the sending system apparatus. This connectionconsists of two circuits, one circuit 21 containing a variable point ofconnection of duces oscillating current in the receiving apparatus whichhas the same frequency as the current flowing in the aerial sendingsystem.

Referring to Fig. 2, this energy is indicatedby vector 25, this vectorrepresenting the electromotive force of the energy which producesinterference in the receiving apparatus to prevent the reception ofsignals from a distant station. This clcctromotive force is neutralizedby an equal electrometive force in precise phase opposition, which maybe represented by vector 20. It is not however, possible to convey thisamount of energy at this phase relation from the sending apparatus tothe receiving apparatus by a single conductor, inasmuch as resistanceloss and'inductive and capacitive effects do not permit of the readydevelopment of an electromotive force at precisely 180 phase difference.

This electromotive force at the proper phase displacement can be readilyobtained, however, by two successive increments of energy. The portionof sending helix 3 which lies below the ground lead connection (5develops an electromotive force which is approximately at a phasedisplacement of 180. A suilicient electromotive force is, therefore,transferred from this lower portion of coil 3 by way of conductor 21 andcondenser 22 to point 19 in the receiving set. This is represented byvcctorZB. This energy will give partial neutralization of theinterfering energy. A further increment of energy represented by vector27 may be conveyed from the sending set to the receiving set to giveprecise neutralization of interfering energy, by means of conductor 23'and variable resistance 24. Adjustment of resistor 24'and condenser 22thus controls the phase relationand the magnitude of the conductivelytransferred electromotive force to the value which gives preciseneutralization of the interference.

In practice, this system of a plurality of 'conductive connectionsbetween adjacent sending and receiving sets transfers energy from thesending to the receiving set which is inprecise phase opposition andequal in magnitude to energy transferred from the sending to thereceiving apparatus by way of their respective aerials and the ether,thereby permitting duplex operation of the sending and the receivingapparatus.

WVhile I have shown only one embodiment of my invention in theaccompanying drawing, it is capable of various changes and modificationswithout departing from the spirit thereof. I desire that it be notrestricted to radio-frequency interference phenomena and that.therefore, only such limitations shall be placed thereon as indicated inthe prior art or in the appended claims.

I claim as my invention.

1. In a -duplex system of radio signaling,

a station comprising a sending apparatus, a receiving apparatus, and aplurality of circuits linking said sending and receiving apparatus, saidsending apparatus comprising an aerial, a tuning helix operativelyconnected thereto, a ground, a metallic connec: tion between said groundand said helix, said connection being made to said helix at a pointother than the bottom turn thereof, and a source oi high frequencyenergy, said receiving apparatus comprising an aerial, a receivinginductance, a ground connection, detecting means, and signal indicatingmeans, a circuit linking turns of said tuning helix below said groundconnection to the junction between said receiving inductance and saidaerial through a variable condenser, and an additional circuit linkingturns of said tuning helix above said ground connection to the samejunction between said receiving inductance and said aerial through avariable resistance.

2. In a duplex system of radio signaling, a station comprising a sendingapparatus, a receiving apparatus, and a plurality of circuits linkingsaid sending and receiving apparatus, said sending apparatus comprisingan aerial, a tuning helix, a metallic ground connection for said helix,said connectionbe ing made to said helix at a point other than thebottom turn thereof, and a source of high frequency energy, saidreceiving apparatus comprising an aerial, a receivinginductance, aground connection, detecting means, and signal indicating means, acircuit linking turns of said tuning helix below said groun-d connectionto the junction between said receiving inductance and said aerialthrough a variable condenser, an additional circuit linking turns ofsaid tuning helix above said ground connection to the same I junctionbetween said receiving inductance and said aerial through a variableresistor,

and additional linking circuits comprising inductive, capacitive,resistive and conductive elements.

3. In a radio system, a sending set including an antenna, a coil andmeans for energizing said coil, a receiving set including an antenna andreceiving instruments associated therewith and means for compeneatingthe efi'ect of the sending antenna on the receiving antenna comprising aclosed circuit connecting twopoints of said coil at opposite potentials,said circuit including a resistor and a reactor in series at least oneof which is adjustable, and a connection from a point in said circuitbetween said re-- sistor and reactor to a point in the receiving set.

In testimony whereof, I have hereunto subscribed my name this 13th dayof August, 1923.

CLARENCE A. BODDIE.

